Contracting flow pattern induced by the staggered arrangement of oscillating fish-like fin propulsors - time-averaged flow structure obtained by 2D PIV measurement-

Herein, three oscillating fin propulsors connected in a parallel and in a staggered arrangement were investigated to develop an environmental-friendly and energy-saving propulsor. In this study, the flow pattern induced by these fish-like propulsors was achieved with a low Reynolds number and was measured using the particle image velocimetry (PIV) technique. In the case of the staggered fin setting (front: 1, rear: 2), which showed a relatively high propulsion performance, the flow pattern detected by multi-sliced 2D PIV was found to be a jet-like contracting flow pattern. On the other hand, results obtained for the parallel setting and inverted triangle formation (front: 2, rear: 1) showed branching flow patterns in the horizontal direction. The results for the jet-like contracting flow patterns suggested the existence of dominant flow patterns, providing a high thrust force with low power relative to conventional fin propulsors.